There are some BB Bastard BB's I left out at the LZ in Ottawa specifically to see what happened to them long term in sunlight. After a couple months they where pitted and by the end of a season they crumbled when I squeezed them hard. They where gone within a yeah, turned to dust.

Bio Degradable BB's are also known to be more brittle and can screw up inner barrels. One local guy at Border War 1 got shot on the edge of his goggles with a bio degradable BB, it shattered and sent the fragments under the goggles into his eye. If it was a standard BB it would have bounced off the edge of his goggles.

well, they have to make Biodegradables easy to shatter. More Surface area = faster decomposition.